A large capacity pressure cooker generally comprises a vat or cooking vessel of a size to receive a wire basket in which the product to be cooked is located. The basket is thereafter immersed in the cooking oil contained in the vat. The vat is closed by a lid which makes a seal with the top of the vat. The product is cooked for the desired length of time under both heat and pressure. Following the cooking cycle, the pressure in the vat is relieved and the lid is opened, whereupon the product is removed from the wire basket. Exemplary large capacity pressure cookers of the type to which the present invention is directed are illustrated and described in U.S. Pat. Nos. 4,930,408 and 4,997,101. During the cooking operation, when the vat is pressurized, it is imperative that the vat lid be firmly closed and locked, as a matter of safety. The above-identified references teach locking mechanisms suitable for this purpose.
A problem arises from the fact that the vat lid must be of heavy construction to properly and safely withstand the pressure within the vat during the cooking cycle. To overcome this problem, prior art workers have devised various types of automatic mechanisms for opening and closing the vat lid. Vertically shiftable rod means for raising and lowering the lid are taught in U.S. Pat. No. 3,187,664. U.S. Pat. No. 3,608,472 is exemplary of a number of patents teaching the use of jack screws or the like. U.S. Pat. No. 3,821,925 teaches the use of a geared bar or rack-like system. U.S. Pat. No. 3,563,158 describes hydraulic cylinders used to raise and lower the vat lid. In some instances, these various mechanisms are used to additionally hold the lid down in place during the pressurized operation of the cooker.
Some of the prior art lid raising and lowering mechanisms required powerful power train means. Many of them required that the lid actuating mechanism be located at the sides or about the vat making access to the vat and cleaning operations more difficult. Many of the electro-mechanical or hydraulic systems used for this purpose have been characterized by maintenance problems and attendant down-time. Some are sufficiently complex as to require a skilled operator. As a result, efforts to mechanize the operation of large capacity pressure cookers by means of electro-mechanical or hydraulic controls for raising and lowering the lids of the vats have produced more problems than they have solved.
U.S. Pat. No. 4,930,408 teaches a different approach. In accordance with this reference, the lid is provided with a substantial locking mechanism to maintain the lid in its seated, closed position during that part of the cooking cycle in which the vat is pressurized. The vat lid is raised and lowered manually, but is provided with a counterbalance system so that the operator need not contend with the full weight of the lid. While this system works well, it still requires some strength on the part of the operator and is more difficult for the smaller operator to handle.
The motorized assist assembly of the present invention uses a cable operated by an electric motor driven cable drum. The motorized assist assembly of the present invention is simple in construction and inexpensive to manufacture. The motorized assist assembly is located at the rearward end of the pressure cooker housing and does not interfere with access to the vat or cleaning of the vat and lid. The assist assembly is very simple to operate and does not require a skilled operator. A safety arrangement of the actuating means for the assist assembly, assuring against injury of the operator, can be employed, as will be described hereinafter.